A method and apparatus are disclosed for forming an image signal by receiving a flux of photons at a convex photodetector such as a hemispherical photodetector. The convex photodetector includes a plurality of photosensors. Each photosensor has a different orientation with respect to a propagation vector of the flux of photons. The photosensors generate a respective plurality of intensity signals. Each of the intensity signals is related to the respective orientation of the photosensor that generates it. The intensity signals are received by a signal processor, such as a digital signal processor, which uses the intensity signals to compute an image signal related to the intensity signals and thereby produce a focused output image.